However, he questioned whether the results accurately reflected support for the incumbent.

"The presidential result as announced do not reflect the genuine expression of the will of the Zimbabwean people given the many anomalies, malpractices, deflation of figures relating to Zanu-PF candidates," he said.

Simba Makoni, a former finance minister, came third in the election with just 8.3 per cent. He is widely expected to back Tsvangirai in any run-off.

The MDC has previously rejected the idea of a run-off and on Friday accused the commission of inflating Mugabe's number of votes by 47,000 and deflating those for Tsvangirai by 50,000.

Tsvangirai 'president'

"Morgan Tsvangirai is the president of the republic of Zimbabwe to the extent that he won the highest number of votes," Tendai Biti, the party's general secretary, told a press conference in South Africa.

Biti said that a run-off could not be held "for the simple and good reasons that that country is burning" amid violence and an economic crisis.

Haru Mutasa, Al Jazeera's correspondent reporting from Harare, said that the MDC considers the 47.9 per cent figure to be "wrong" and that it "should have been in the fifties".

"They [opposition] are saying that the ZEC rigged the numbers to ensure that there is a run-off," she said.

"They also saying that if they take part in the run-off they will not be allowed to campaign freely and that their supporters would be further intimidated [by security forces]."

Under the terms of the constitution, Mugabe would be declared the winner if Tsvangirai did not take part in a second round.

In Washington, a US state department spokesman said that the results had "rather serious credibility problems" and doubted a run-off would be free and fair.

'Political violence'

On Friday, Thabo Mbeki, the South African president, told religious leaders that he would send a mission in Zimbabwe to investigate reports of politically related violence.

"He assured us that he would do everything to ensure that a second round of the run-off election happens in an atmosphere of peace," Nyansako Ni-Nku, head of the All-Africa Conference of Churches, was quoted by the SAPA news agency as saying.

Human rights groups have accused the government of using the army and so-called "war veterans" of using the delay in publishing the results to intimidate opposition supporters before a possible run-off.